The use of optical fibers for the transmission of data is becoming more and more prevalent in the field of telecommunications. Telephone companies, cable companies, and internet service providers, for example, are continually expanding their fiber optic networks to reach more consumers over a larger geographic area.
Optical fibers have several advantages over traditional metallic communication lines. Optical fiber has the capacity to transmit more data than metallic wires due to greater bandwidths. Optical fiber transmission is also less susceptible to interference from external signals. Due to optical technology developments in the last decade, optical transmission has further un-regenerated reach than traditional electrical transmission.
Optical fibers can be installed in underground or overhead constructions. For example, fiber optic cables may be buried directly in trenches, installed in underground conduits, inserted in paved streets, or inserted into the ground wire for high-voltage power lines. As a result, installed fiber optic cables may be prone to damage in the field from environmental hazards, such as construction work or gnawing animals. In addition, precise location of underground optical fibers and splice points is a significant challenge, and poor location of fiber and fiber splices can be expensive.
When part of an optical network fails due to damaged optical cables, it is essential that the damage can be quickly and accurately located to minimize the duration of the outage and to minimize the cost of repair. In many installations, cables are equipped with location “tones” that carry an electromagnetic signal along a metal conductor within the optical fiber cable. These tones can be detected from above ground and may facilitate the general location of a cable. However, location tones are generally not applicable for fiber splice points. Furthermore, in some older constructions, metallic wires carrying location tones may not have been deployed with the original fiber optic cable, or the metallic wires may have broken connectivity through corrosion or other damage.
In these instances, the location of the optical fibers may be manually sketched or recorded on area maps by the technicians initially installing the cables or subsequently performing maintenance or repair work. Manually recording the location of the cables in this way, however, increases the risk of recording inaccurate or vague location information. For example, a line drawn on a map meant to represent a fiber optic cable may not be drawn in the exact location on the map corresponding to its actual location in the ground.
In engineering new optical systems on older fiber, it is frequently necessary to repair existing splices and other links between fiber optic cables. Technicians called to the field to repair or modify fiber splices generally rely on the manually produced maps to identify the proper location to dig for the cables. Because most underground optical fiber cable is buried adjacent to railroad tracks, digging becomes very expensive due to the large contract crews necessary to flag the railroad and traffic. A failed attempt to locate a fiber optic cable thus results in increased costs due to longer service times as well as the cost of restoring the improperly excavated area. A failed attempt also results in the opportunity to damage other underground equipment that may be buried where the fiber optic cable was thought to be located.
Engineering and planning groups are also responsible for instructing others as to the location of the underground network. For example, a construction crew may need to know the location of communication lines and equipment buried in the vicinity of a construction site in order to avoid damaging the network. Inaccurate location information increases the risk that underground lines will inadvertently be damaged in the course of construction and leads to unnecessary and costly repairs and litigation.
Efforts have been made in the past to more accurately measure and record the location of underground fiber optic cable. One method that has been attempted is to provide every technician with a hand-held global positioning system (GPS) device to obtain precise coordinates corresponding to the location of the technician and, in turn, the fiber optic cable being installed or serviced. The provision of GPS devices to technicians, however, has been found by many in the industry to be an unpractical and cost prohibitive approach to solving the problem of locating underground cables. In addition to the cost associated with the purchase of individual GPS devices for every technician and the inconvenience to the technicians of carrying and maintaining one more piece of equipment, the devices are not simple to operate and require the technicians to undergo additional training. Also, the process of recording the location of the fiber optic cable using a hand-held GPS device still involves action by the technician to obtain coordinates at the correct physical location and to then manually record those coordinates on the proper form. Thus the possibility of human error is still present.
Therefore, there is a need for systems and methods to simply, accurately, and reliably obtain and record the geographic coordinates of underground fiber optic cables and splices in a manner that allows more location information to be recorded, reduces the possibility of error, and provides greater accessibility to the location information associated with different parts of the optical fiber network.